(1) m is between 40 and 80.

Consider m= 45 this gives us YES

Consider m= 79 this gives us NO

(2) m is between 50 and 90

Consider m= 55 this gives us YES

Consider m= 79 this gives us NO

Combining both gives us YES and NO

So E
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Target question: Is m between 35 and 75 ?

Statement 1: m is between 40 and 80
This statement doesn't FEEL sufficient, so I'm going to TEST some values.
There are several values of m that satisfy statement 1. Here are two:
Case a: m = 55, in which case m IS between 35 and 75
Case b: m = 76, in which case m is NOT between 35 and 75
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: http://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: m is between 50 and 90.
Let's TEST some values.
There are several values of m that satisfy statement 2. Here are two:
Case a: m = 55, in which case m IS between 35 and 75
Case b: m = 76, in which case m is NOT between 35 and 75
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
There are still several values of m that satisfy BOTH statements Here are two:
Case a: m = 55, in which case m IS between 35 and 75
Case b: m = 76, in which case m is NOT between 35 and 75
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent
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